The invention is particularly well suited for use in truck tires and is directed to a mechanism for improving the traction of a partially worn tread.
Briefly stated, the invention is in a pattern of ribs and grooves provided in the tread of a tire. At least one of the grooves includes a ledge intermediate the enclosed bottom and open top of the groove. At least one slot is disposed in the ledge to increase traction of the tread on the roadway when the ribs adjacent the groove are sufficiently worn that the ledge contacts the roadway.